(defun dired-repeat-over-lines (arg function)
  ;; This version skips non-file lines.
  (let ((pos (make-marker)))
    (beginning-of-line)
    (cond
     ((> arg 0)
       (while (and (> arg 0) (not (eobp)))
         (setq arg (1- arg))
         (beginning-of-line)
         (while (and (not (eobp)) (dired-between-files)) (forward-line 1))
         (save-excursion
           (forward-line 1)
           (move-marker pos (1+ (point))))
         (unless (eobp)
           (save-excursion (funcall function))
           ;; Advance to the next line--actually, to the line that *was* next.
           ;; (If FUNCTION inserted some new lines in between, skip them.)
           (goto-char pos)))
       (when (eobp)
         (forward-line -1)
         (dired-move-to-filename)))
     ((< arg 0)
       (while (and (< arg 0) (not (bobp)))
         (setq arg (1+ arg))
         (forward-line -1)
         (while (and (not (bobp)) (dired-between-files)) (forward-line -1))
         (beginning-of-line)
         (when (condition-case nil
                 (dired-get-filename)
                 (error nil))
           (save-excursion (funcall function))))
       (move-marker pos nil)
       (dired-move-to-filename)))))

(defun dired-between-files ()
  ;; This used to be a regexp match of the `total ...' line output by
  ;; ls, which is slightly faster, but that is not very robust; notably,
  ;; it fails for non-english locales.
  (not (condition-case nil
         (dired-get-filename)
         (error nil))))